In the past 20 years, the total amount of microplastics deposited on the seafloor has tripled, corresponding to the consumption type and quantity of plastic products. This is the main conclusion of a study carried out by the Institute of Environmental Science and Technology of the University of Barcelona in Spain and the Department of Building Environment of the University of Aalborg in Denmark. This study is the first high-resolution reconstruction of micro plastic pollution caused by sediments in the northwest Mediterranean.

Although the seabed is considered as the final sedimentation tank of micro plastics floating on the sea, the historical evolution of this pollution source on the seabed, especially the storage and burial rate of small micro plastics on the seabed, is still unclear.

This new study, published recently in the journal Environmental Science and Technology, shows that microplastics remain unchanged in marine sediments. The quality of these microplastics simulates the global plastic production from 1965 to 2016.

The researchers applied the most advanced imaging technology to quantify particles with a size of 11 microns, and investigated the degradation state of the buried particles. They found that once the microplastics were trapped on the seafloor, they would no longer degrade.

Research shows that the number of plastic particles deposited on the seabed has tripled since 2000, and with the production and global use of these materials, the cumulative number of plastic particles has been growing.

The researchers explained that in the past 20 years, the accumulation of polyethylene and polypropylene particles in packaging, bottles and food films, as well as the accumulation of polyester particles in synthetic fibers in clothing fabrics, has been increasing. In each kg of sediment collected, the content of these three kinds of particles reached 1.5 mg, with the highest content of polypropylene, followed by polyethylene and polyester.